Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sun-barr!lll-winken!taco!hobbes.catt.ncsu.edu!kdarling From: kdarling@hobbes.catt.ncsu.edu (Kevin Darling) Newsgroups: comp.sys.amiga.graphics Subject: Re: 24bit display questions Message-ID: <1991Jun28.235811.9143@ncsu.edu> Date: 28 Jun 91 23:58:11 GMT References: <1991Jun21.002446.3856@menudo.uh.edu> <1991Jun21.134816.10190@uokmax.ecn.uoknor.edu> <1077@celia.UUCP> Sender: news@ncsu.edu (USENET News System) Organization: North Carolina State University Lines: 52 > I am not I understand the Colorburst device. It claims to be a true 24-bit > display device with 1.5 megs onboard, yet the signal comes through the > RGB port. I was not aware that data could be passed through the RGB port. > Is this possible? If it is, it is not bi-directional, right? Right, it's unidirectional. These "outside" devices convert the RGB pixel output of the Amiga hires 16-color screen back into 4-bit values, then usually recombine those nybbles into bytes for further use. Clever. > DCTV seems to be a decoder, with the display memory being in the Amiga. > This makes sense. The Colorburst does not. Yes, that's correct. HAM-E and DCTV both decode and display the Amiga vidram output info in more or less realtime. Colorburst has its own buffer(s), which are updated via the Amiga output. I believe that: HAM-E has its display memory in the Amiga. It directly takes the output, combines it into bytes, decodes into either 256 or "HAM-Extended" colors. Therefore every pixel is displayed "immediately" (in 2 hires pixel time). DCTV also uses the Amiga vidram as its memory, altho pairs of output lines are combined to obtain the full info to display both the lines. That is, each even line contains the even line's luma and 1/2 the chroma info used for both lines; each odd line contains the odd line's luma and the other 1/2 of chroma info to be used for both lines. Colorburst uses the Amiga memory more indirectly... as a transfer buffer. This makes sense, as a 320x200x24-bit image (for example) would require 192K of info. So (in the above case), three Amiga display fields are used to send out first the R, then the G, then the B data. Or other info. But it stores the data in its own display memory. > Is there a way to get the data from the Colorburst into the Amiga? > Would it use the parallel port like DCTV? Umm. No need to. It's just an output device, and the info is already in Amiga memory (or was at the time of transfer :-). > I have worked in computer graphics for years, but until recently I have > never seen such a strange, yet ingenious assortment of frame buffers as > the ones available for the Amiga. I guess it's what you get when you have > graphics so tightly coupled to a system. I guess it is whatever works.:-) Yah. Actually, they could've used the video or bus slots (like Framegrabber and Firecracker). But the common RGB port was appealing, partly because of no card size restrictions, plus it allows easier sales for all Amiga models. It occurs to me that these devices could probably be used on any computer because of the way they attach. For that matter, someone could build a fairly simple output buffer onto a Zorro card, and boost the amount and/or speed of animations through these devices. You'd have to write your own software, of course. best - kev